Engine driven RSW systems

[dellori3]

I am here to provide guidance in Refrigerated sea water systems (RSW) for salmon troller’s. My background consists of 50 years as a salmon Troller; much of that was part time. After retiring from refrigeration and air-conditioning, Lori and I fished full time.

I installed my first RSW system some 30 years ago and have done many boats since. You will note I said Salmon Troller; If you are a net boat in Alaska, I am not your guy which also applies to all tuna boats. You will need a much larger system then. My systems consist of an engine driven automotive 4- ton compressor (SANYO SD508 or 10), a custom condenser mounted in line with engine heat exchanger or an option keel cooler. In the fish storage box I have stainless serpentine coils. The target RPM for compressor is 1,000.


Post your questions and I will get back ASAP.


Del

[Drew]

So would this kind of system be for the hold or for pre-chilling before icing? I've often thought a kind of RSW rinse bin would be a cool thing to have.

I don't always do this, but I have on occasion, slushed fish before icing them. It's amazing when you go to unload and none of the ice in their bellies has melted and is still perfect flakes.

[dellori3]

Drew,no this system replaces ice all together. It starts with clean sea water and refrigerates it down to 29 degrees by building an Ice bank on the coils.
After bleeding,gut and giiled the fish is dropped into the cold sea water for storage till off loading.
Fish handled this way are very pristine and have a longer shelf life.
dellori3

[Trnaround]

Delori3, I can sure see the advantages in Refrigerated Sea Water (RSW), in getting away from ice having always iced or slushed fish. Unless it's changed in Alaska the processors that I have dealt with only want iced or slushed fish because of their concerns with scale loss. In rolling seas even improperly slushed fish (too thin slush mix) can cause this and results in a fish being seconded. Are their ways of taking care of this problem or are there differences in what is acceptable in different areas?

[Zedlander]

How much power does an RSW system use? The couple of people I know who use this set up have to have another engine just to run the RSW. Is this still the case? Thanks

[dellori3]

On a Salmon Troller the size of the system only needs to be on the order of a/c unit from a large car it uses the very same compressor.
That being the case it will consume around 2 to 4 HP from the main engine @ 1,000 RPM. It will stay up with a 100 fish day (kings). Do you know many high liners that exceed that?
Scale loss is at a minimum especially in deep boxes and all fish face forward.
Dellori3

[dellori3]

[dellori3]

RSW condenser—there are three different ways of doing this 1-Keel cooler a through hull to direct contact under the boat. 2-tube in tube water condenser requires a pump. 3- Shell and tube in line with main raw engine cooling water. Of the three I prefer the shell and tube with full water flow required for the main engine. In the state Washington and above, pipe it after the main heat exchanger to add some temperament to the colder sea water. Below Washington and especially California, pipe ahead of the main heat exchanger.
The condensing tempiture is an important factor as it determines the pressure across the TXV and is directly related to the amount (tonnage) of refrigerant the valve will meter.
dellori3

[Zedlander]

I am sure this varies with each vessel, but roughly, what is the cost of installing an RSW system? A boat that is set up to slush fish. Thanks for the information too, I appreciate it.

[dellori3]

Zedlander, It depends on how much of the work you can do yourself. $2K to 3K would be ball park.
dellori3

[Crawfish]

Delori3, I can sure see the advantages in Refrigerated Sea Water (RSW), in getting away from ice having always iced or slushed fish. Unless it's changed in Alaska the processors that I have dealt with only want iced or slushed fish because of their concerns with scale loss. In rolling seas even improperly slushed fish (too thin slush mix) can cause this and results in a fish being seconded. Are their ways of taking care of this problem or are there differences in what is acceptable in different areas?

If the tank is setup right this is a non issue as the coils are typically covered by an ice bank so they are smooth. The way my system was built the fish would not get up to the coils typically until two days into a trip and by then they had an ice bank. On a properly built system the fish will be absolutely beautiful when you unload. Plus side to refrigeration is when you fuel up you go fishing. No more waiting in the ice line, no more broken ice machines, if they are biting hard you don't run out of ice. Downside is when your system breaks your sol and it could cost you a trip unless you go buy ice or get it fixed fast enough. When you leave the dock with ice you know what you have. With refrigeration it does not take long to lose your ice bank if your system fails, maybe a day and then it's game over.

I have had refrigeration and it has payed for itself time and time again over the years. I highly recommend a 134A DIY system.

[dellori3]

Crawfish in right on with his comments... The design of the fish storage box is a very important part of any RSW system. A deep box and a center divider provide the best product.
dellori3

[dellori3]

Picture 189.jpg

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deep box
dellori3

[dellori3]

Typical engine driven RSW compressor installation. Note the compressor can be driven in either direction.

[dellori3]

Clutch wireing

[thediverdude]

I am a small california day troller. Ice is an issue. Only hold 200 pounds and have to pay for 400 lbs. an RSW sounds ideal. How long does it take to chill? Can a electric compressor be installed in parallel to pre-chill the water while at the dock overnight?

[Crawfish]

I am a small california day troller. Ice is an issue. Only hold 200 pounds and have to pay for 400 lbs. an RSW sounds ideal. How long does it take to chill? Can a electric compressor be installed in parallel to pre-chill the water while at the dock overnight?

On a properly sized system you can pull water temps down to around 30 degrees in six hours of running. Trolling it may take a full day. It really depends on how many ton system you install, how many fish you put in your tank ...

If you have a small tank you may want to look at a externally mounted chiller of sorts. The coils do take some room in your tank. A small tank will lose a fair amount of holding volume with coils. Placing an external evaporator may make the most sense. Some guys with remote mounted chillers recirculate the water with the large rule wash down pumps.

On a side note some guys in the past have used a 5 gallon bucket as their condenser as a cost savings measure and ran their deck hose into the pail of copper coils. Junk yard ac compressors will work fine or you can buy a new one. Proper lubrication oil and correct amount of oil in your system is paramount.

Pre chill might be a good option for your situation. Designed properly running compressors in series can be done.

[dellori3]

The beauty of this system is this: I would leave the slip with the fish hold completely EMPTLY. I DID NOTHING TILL I CAUGHT MY FIRST FISH. Then I would turn on the switch for the compressor and fill enough water to cover the two bottom pipes. We added fish and water in a amount to just cover the fish and when we had a ice bank (2 inches) built up we would shut off the compressor until we had a big pumper on, I would start it again and the boat would slow down just a little till we got him - her in the kill box. That’s the way the days fishing would go. I would take notice of the ice bank at all time and maybe we would need to run it more often if we were catching a lot of fish. Near the end of the day I would decide what to do depending on weather we were off loading or making a trip of more days fishing. As long as I had an ice bank I didn’t worry till some time next day.
dellori3

[dellori3]

One of the problems I encountered when I built my original RSW system was the condenser. There was not a desirable one made for boats running off the main engine. As a result of this I designed a full flow one using all the engine cooling water without creating a restriction for the main engine. Protected with no 2 zinc and a cleanable brass cap. The condenser would match up to 250 HP engine cooling systems. On larger engines it may be necessary to parallel the condenser by installing a ball valve in the main line and throttle it down till you have equal flow or the correct amount of water flowing through the condenser.
dellori3

[Crawfish]

dellori3,

Is that a transmission style heat exchanger with JIC fittings soldered on it?